Using electro-reduction method produce bronze phase tungsten oxide is a common method. Using electrochemical reaction restore WO3 and molten alkali metal tungstate. Generally use carbon as the anode, Pt or CrNi alloy as a cathode, the producing process is expressed as follows: x / 2Na2WO4 + (1-x) WO3 → Na2WO3 + x / 4O2. in sulfuric acid solution electrolytic reduction  WO3 can produce a series of HxWO3 bronze, after that a number of scholars have used WO3 or bronze as electrode material to produce (NH4) 0.3HxWO3, H0.6WO3 and other bronze. Although the method be used widely but high equipment requirements, and greater energy consumption.

There is another method which is using electrochemical produce tungsten bronze phase, and that is ion insertion method. This method is through electric field putting suitable ionic radius into the pores to form tungsten oxide bronze, and it can produce a bronze phase tungsten oxide which has two kind of ions simultaneously existed. This approach can greatly reduce the reaction energy consumption, but also improves the efficiency of the reaction.

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Study tungsten oxide photochromic almost half a century, but uncertainty and change color to characterize the unity of the light source chosen their development will be very slow. 1973 Deb use Urbach rule: K (v, T) = K₀exp [-B (E^Ω_g-hv) / KT]. Where hv is radiant energy, B and K₀ is a constant characteristic of the material. When the light energy is more than 3.5eV, the (Khv) ^{L / 2} and hv will be a linear relationship. That K is proportional to (hv-E^Ω_g) ² / hv. Accordingly reasoning greenhouse condition the energy band gap is3.25eV. Because the selection is a suitable light source, it is the key to discoloration. Currently there are reports of high pressure mercury lamp light source and two high-pressure xenon lamps. However, the use of light source wattage vary, mercury has 500w, 400w, 250w, 150w and the like. Xenon lamps have 500w, 200w, 150w, 75w, etc. Although only change the wattage of light intensity, but it reflects the color properties of tungsten oxide. In particular, to meet the different needs from the standpoint of photochromic material when under sunlight sunglasses manufacturers have been the most demand, high-band color and Zeng field of information needed for long-term stable material, and display material aspect requires fast coloring and bleaching properties.

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In fact, heat reduction method is the general term of many ways. Using production bronze phase tungsten oxide as example, there are solid - solid state reaction, the solid - molten reaction, gas - solid state reaction, thermal decomposition reaction and hydrothermal dissolution reactions and so on. In addition to hydrothermal and solvothermal reaction method, several other production methods require at higher temperature and reducing atmosphere, and this will inevitably increase the requirements for instruments and high energy consumption, difficult to control the reaction, the reaction process is easy appeared mixed phase. Therefore, it is not the best choice for producing bronze phase tungsten oxide. The hydrothermal and solvothermal synthesis method has many advantages which get more and more people's attention. some researchers using glacial acetic acid and ethylene glycol as a solvent, and in autoclave which having lined stainless steel for 5 days at 200 ℃, the (NH4) 10W12O41 reduced to sixty thousand bronze with (NH4) xWO3.

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Tungsten crucible is the product of tungsten. Forging tungsten crucible refers to tungsten crucible is made through unwrought, whose purity can reach to 99.95% and density is up to 19.1g / cm3. Sintering tungsten crucible size is larger than the forging one, it can achieve the maximum diameter of 100mm, a thickness of 5 ~ 12mm, height up to 100mm.

Forging tungsten crucible is mainly used for smelting metals, such as, molten aluminum. Forging tungsten crucible’s density (can reach to 19.1g / cm3) is different from Sintering tungsten crucibles’ (18.2/cm3) in physical properties. Forging tungsten Crucible has a better crystal structure. Because of its high temperature resistance, it can be used as core container of rare earth smelting furnace and other industrial furnace.

Physical properties of forging tungsten crucible:

High purity;

High density;

No internal cracks;

Size precision;

Smooth inner and outer walls.


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